I believe that you are referring to the fog light on your X1. It's a simple fix if the bulb has just burned out.
Find the procedure here: https://www.newtis.info/tisv2/a/en/
Replacement bulbs are available at your dealer, the online BMW parts houses (FCPEuro is my fav) and even Amazon.

If it is the fog light, the bulb and / or housing is pretty cheap. The drivers side on mine got smashed out driving the car home when I first bought it, so I had to buy a whole new fog light assembly (the glass housing) and the cost was ~$125.00. They're not that expensive.